Ultrasonic welders are known in the art. Known welders suffer several deficiencies in use. First, they are typically not capable of automatically calibrating either the physical or electrical weld parameters. Second, they do not very efficiently convert ultrasonic energy to weld energy.
Prior devices typically require manual calibration for each different weld zone size and material to be welded. This manual calibration must be repeated each time it is desired to weld either a different amount of material or a different material. For example, in ultrasonic welding of copper wire, changing to wire of different gauge will require recalibration of the welder. Calibration requires adjustment of not only physical parameters such as the positions of support, anvil and gathering tool as disclosed in U.S. Pat. No. 4,867,370, but also electrical parameters such as weld time.
Manual calibration makes operating ultrasonic welders expensive and disadvantageously reduces their usefulness in manufacturing environments either where multiple welds of varying size or material need to be made on a single product or subassembly, or where there are frequent line changes of products to be welded.
More recent ultrasonic welders have also been equipped with error detection features which confirm whether a particular weld matches the current calibration for the machine. These devices, however, are not capable of automatic recalibration when a mismatch is detected.
Further, it is suggested to automatically adjust the size of the weld chamber by a predetermined ratio. German Patent 4,335,108C1 dated May 1, 1995 discloses a welding apparatus with a weld chamber that contracts when the width and height of the weld chamber moves at a predetermined ratio. Similarly, U.S. Pat. No. 4,869,419 to Nuss discloses a similar welding apparatus. Where the ratio of height to width is maintained relatively constant, for large welds, the height of the weld is excessive. More particularly, the height of the weld is the distance between the surface of the welding tip that is in contact with the wires and the anvil opposite the surface of the welding tip. When a predetermined ratio is maintained, the height for large welds can be excessive and result in inadequate welds.
A further disadvantage of the prior art is that weld parameters are stored. Thus, large amounts of data must be stored, making the storage medium and the microprocessor unduly complex. It would be desirable to provide a device that does not necessarily rely on stored data for weld parameters.
It is known to be desirable in ultrasonic welders to tune the horn to the transducer and to mount the horn coaxially with the transducer for maximum efficiency. It is also generally known that the horn must be supported, preferably at its nodal point, in order to prevent loading of the tip by the anvil from deflecting the horn off the transducer axis. In prior welders, the horn is typically rigidly mounted by set screws on its nodal point while at rest.
With such mounting systems it is often disadvantageously difficult to accurately align the horn on the transducer axis. More importantly, however, when the horn is in use its nodal point shifts with the longitudinal vibrations so that prior rigid mounts are rarely located at the nodal point with the horn in use and thus disadvantageously absorb significant energy, reducing the amount transmitted to the weld.
What is desired, therefore, is an ultrasonic welder capable of automatically recognizing and welding variable size and type articles. An ultrasonic welder with a dynamic horn mount which absorbs less, and thereby transmits more transducer energy to the weld, is also desired.